- Email: [email protected]
Glucose concentration gradients across the maternal surface, the placenta, and the amnion of the rhesus monkey (Macaca mulatta)
Glucose concentration
gradients across the
maternal surface, the placenta, and the amnion of the rhesus monkey (Macaca mulatta) FREDERICK ANDRE
C. E.
CHRISTOPHER RICHARD Baltimore,
BATTAGLIA,
HELLEGERS, J.
M.D.* M.D.+*
HELLER,
BEHRMAN,
A.B.
M.D.*
Maryland
A s P A R T of a study of the primate placenta, determinations of oxygen and carbon dioxide concentrations in fetal blood and in the maternal arterial and venous blood perfusing the maternal surface of the placenta of the pregnant Macaca mulatta have been made and are reported e1sewhere.l Simultaneously, determinations of plasma glucose concentrations in those same animals were made. It is the purpose of this report to present the data on glucose concentrations and to correlate these data with those on the placental exchange of the respiratory gases in the same preparations. In addition, glucose concentration gradients between the amniotic fluid and either the maternal or fetal vascular pool at varying stages of gestation are presented.
First, even in the acute preparations, if due care is taken, the glucose concentrations? per se, may closely approximate the normal steady state values. The importance of such information for any solute has been discussed elsewhere.’ Finally these studies, combined with the oxygen and CO, data presented in the preceding article, were undertaken to provide a more complete evaluation of placental function than has heretofore been possible in the conscious primate under minimal experimental stress. Material
From the Departments of GynecologyObstetrics, and Pediatrics, The Johns Hopkins University and the Department of Gynecology-Obstetrics, University of Puerto Rico. This study was supgorted in part by Research Grant AM-O4240-03 of the National Institutes of Health. *Member, Laboratory of Perinatal Physiology, National Institute of Neurological Diseases and Blindness, National Institutes of Health, San Juan, Puerto Rico.
“*Senior P. Kennedy,
Research Scholar, Jr., Memorial
and
methods
The studies were carried out at the Laboratory of Perinatal Physiology, San Juan, Puerto Rico. The monkeys were selected from a large breeding colony of caged animals on the basis of gestational ages. The criteria used for the gestational timing and selection were as outlined e1sewhere.l The previous report also describes in considerable detail the operative technique. It should be emphasized that variations in operative technique were found to be equally critical for the establishment of normal glucose gradients. Further, normal gradients cannot be obtained under conditions of hypoventilation, starvation ketosis, and stress hyperglycemia. The experiments presented in this report were carried out to determine as closely as
Joseph Foundation. 32
Volume Number
88 1
possible, in an acute preparation, the normal gradients for plasma glucose concentrations across the maternal surface and across the placenta as a whole. Hence, the experiments the data of which form the substance of this report were selected out of all our preparations on the basis of criteria encompassing a clinical appraisal of the animals’ condition before and during the experiment, as well as a biochemical appraisal reflected by pH, pCOo, and oxygen content gradients. A more complete description of these criteria and a presentation of the relevant oxygen, CO,, and pH data obtained from the same animals is given in the preceding article. For the determination of the glucose gradient between the amniotic fluid and the maternal vascular pool in early gestation, amniotic fluid samples were obtained from the long saphenous vein. Term amniotic fluid samples were obtained at the time of cesarean section under direct vision and the simultaneous maternal blood samples were taken from a uterine vein. Plasma glucose concentrations were determined calorimetrically, with glucose oxidase as follows: 100 ~1 aliquots diluted 1:40 with distilled water were deproteinized with barium hydroxide-zinc sulfate by the method of Somogyi3 To 1 ml. of the filtrate was then added 4 ml. of glucose oxidase solution (Worthington Biochemical Corporation’s “glucostat” diluted to final volume 80 ml.). After incubation for 30 minutes at 38’ C. the samples were read at 420 rnp on a Beckman model B spectrophotometer. Results
Maternal arterioverous differences and transplacental gradients. The data for arteriovenous differences and transplacental gradients are presented in Table I. In experiments 1 through 5 the maternal uterine vein concentrations of glucose ranged from 102.1 to 131.5 mg. per cent and the femoral artery glucose concentrations ranged from 132.0 to 151.5 mg. per cent. In two additional animals included in Table I, Q 200 and V 798, although other criteria for a good preparation were met, there were very
Arteriovenous
differences
of glucose
33
high elevations in maternal plasma glucose concentrations, probably related to endogenous epinephrine release. The close agreement in maternal venous glucose concentrations between animals caught with minimal agitation, which were sampled immediately after capture without the use of local anesthesia (Table IV), and those which were sampled within one-half hour after incision at the time of an acute term experiment (Tables I and III), done under local anesthesia (2 per cent procaine, without epinephrine), suggests that in most cases the hepatic mobilization of glucose in the mother was not significant. Five of the experiments (9 through 13) presented in Table I did not meet the criteria for a good preparation and have not been used for calculating normal concentration gradients. In the good preparations the fetal umbilical artery glucose concentrations ranged from 89.0 to 157.5 mg. per cent (Tables I and III). In all such cases the fetal umbilical artery concentration was less than either the maternal arterial or venous concentrations. This was not true for experiments 9 through ,13. The maternal arteriovenous differences for glucose in experiments 1 through 8 ranged from 5.0 to 28.0 mg. per cent with a mean of 14.9 ? 8.8 mg. per cent. Although the number of observations is limited, no obvious correlation between the magnitude of these arteriovenous differences and the absolute arterial or venous concentrations was found. However, Table II shows that if all the data of Table I are used, the arteriovenous differences in preparations with maternal arterial concentrations greater than 200 mg. per cent were significantly greater (28.6 vs. 11.6, P < 0.05) than in the remaining preparations. Within each group no close correlation between the magnitude of the arteriovenous differences and the maternal glucose concentration could be found. The plasma glucose concentration gradient across the placenta as a whole, (the transplacental gradient), was calculated from equation 1.
34
Battaglia
et al
( 1) J/1 [MA + Mv] - Fd = transpiacental gradient Since it might reasonably be expected that the glucose concentration in the fetal capillaries of the placenta was higher than the umbilical arterial concentration, the gradients thus calculated probably represent maximum values. In experiments 1 through 6, the gradients found ranged from 12.3 to 43.7 mg. per cent with a mean of 26.6 it 12.8 mg. per cent (Table I). The variations found could not be correlated with any clear-cut difference in these preparations. However, the common feature of experiments 9 through 13 was the marked variability of the transplacental gradient ranging from 63.2 mg. per cent to 31.3 mg. per cent. From this group of unsatisfactory preparations, only experiment 11 had a “TP” gradient within the normal range, and in this case the arteriovenous difference was larger than any in the normal group.
Glucose concentration differences between amniotic fluid and maternal or fetal vascular pools. Term maternal uterine vein glucose concentrations (Table III, 133.4 mg. per cent), were very similar to the saphenous vein glucose concentrations obtained from animals at 95 to 136 days’ gestation (Table IV, 132.9 mg. per cent). These values did not vary over the duration of
(appoxiniate transplacentol 26+6mTm% (.., 3omgm Xl
: i (-tra#~n across
gradient)
AHNIOTII; ePPLS-----7’-------------dlLlTElWAC gfodient amnlan) i
Transplacental
Fig. 1.
gestations sampled. There was no demonstrable relationship between amniotic fluid glucose concentrations. and maternal plasma However, the glucose concentration in the amniotic fluid early in gestation ranged from 64.0 ma. per cent to 91.5 mg. per cent with a mean of 79.2 + 11.2 mg. per cent compared to term glucose concentrations in the amniotic fluid ranging from 44.5 mg. per cent to 65.0 mg. per cent with a mean of 55.9 t 9.2 mg. per cent. The difference between early amniotic fluid and term amniotic fluid glucose concentrations was 23.3 mg. per cent. This difference was statistically significant (p = < 0.01) One animal, I 193, was sampled at 101 and 115 days’ gestation during which time the amniotic fluid glucose concentration fell from 74.5 mg. per cent to 66.5 mg. per cent. Since the glucose concentrations in the maternal plasma did not differ in the two groups, the maternal vein minus amniotic fluid differences were higher at term, reflecting a decreasing amniotic fluid glucose concentration as term approached. The gradients from the maternal saphenous vein to the amniotic fluid between 95 and 136 days’ gestation ranged from 27.5 mg. per cent to 93.5 mg. per cent with a mean of 53.6 rf: 21.2 mg. per cent. In contrast gradients between maternal uterine vein and
Q@ AMNIO TIC lcwlcaltratian gradtent acmss chdaamnian )
ci3nZatian
prodlent
. : ! Wm.
Volume Number
88 1
Arteriovenous
Table I. Plasma and transplacental
glucose
Cestatioflal aqe
Animal Good
Bad
preparations 1. v 195 2. X 692 3. x 590 4. Q 192 5. H 220 6. X 624 7. Q 200 a. v 798
153 157 158 155 155 153 155 153
preparations 9. 543 B 10. X 706 ii. Q 178 12. X 617 13. x 292
*All tMA, femoral
Table II. difference
are artery; vein;
Animal
No.
<
200
(
195 692 590 220 617
Mean SD+
mg.
No.
/
133.5 146.0 132.5
128.5 131.5 125.0 102.1 130.5
1 la.5 95.0 89.5 89.8
Mean SD z!z *Glucose concentrations tMv, maternal uterine
12.5 43.7 39.2 12.3
21.5 25.5
150.5 305.0 170.5 90.0 193.5
Mean SD k
12.5 28.5 14.9 +a.8
26.6 212.8
134.5 253.5 158.5 102.0 232.5
56.0 23.5 35.5 9.5 15.5
44.0 63.2 29.5 -7.3 -31.3
arterial
glucose
concentration
70
5.0 14.5 7.5 21.5 9.5
132.6
11.6 k6.6
Animal
Mvt
No.
>
difference
between
maternal
arteriovenous
200
)
:! 72908” 543 B X 706 x 292 Q 178
differences
A-V,
with
MA A-V
/
TPt (Glucose)
5.0 14.5 7.5
236.0 193.0
MA
153 157 158 155 153 155
arteriovenous
157.5
133.5 146.0 132.5 151.5 99.5
Gezf;
of glucose
A-V?
Fat
expressed in mg. per cent. Mv, maternal uterine vein; Fn, fetal umbilical artery; TP, Tramplacental glucose gradient = MA + Mr - Fn. 2
Table III. Glucose concentration* and fetal vascular pools at term
v 195 X 692 x 590 H 220 X 624 Q 192
Maternal
Mvt
p
Animal
at term:
Mat
206.5 328.5 205.5 99.5 209.0
Correlation of maternal across placenta MA
gradients
151.5 183.0 248.5 221.5
155 152 157 155 156
glucose concentrations maternal femoral artery and uterine
v X x H X
concentration*
differences
mg.
7%
MA
A-V
248.5 221.5 206.5 328.5 209.0 205.5
12.5 28.5 56.0 23.5 15.5 35.5
236.6
28.6 tl5.8
0.05
<
between
fluid
and maternal
Fnt
AFt
i 28.5 131.5 125.0 130.5 183.0 102.1
118.5 95.0 89.5 98.0 157.5 89.8
65.0 45.0 56.0 44.5 64.0 60.7
+53.5 +50.0 +33.5 +53.5 +93.5 +29.1
+ 63.5 + 86.5 + 69.0 + 86.0 +119.5 + 41.4
133.4 k26.6
108.1
55.9 + 9.2
+52.2 t22.8
+ 77.7 2 26.4
in mg. per cent. vein; Fa, fetal umbillioal
j
amniotic
artery;
AF,
amniotic
fluid.
1
(FrAF)
/
(MTAF)
35
36
Battaglia
January 1, 1964 Am. J. Obst, 6’1 Gynec.
et al.
Table IV. Glucose concentration” differences between amniotic fluid and maternal vascular pools in early gestation
Animal No. J V I I x L J
89 196 193 193 470 248 394
Mean SD k
Gestational age Cdavs) 95 100 101 115 123 125 136
M,+
AF+
/MT-AF)
128.0 118.0 129.0 114.5 145.5 157.5 137.5
91.5 90.5 74.5 66.5 82.0 64.0 85.5 ___
36.5 27.5 54.5 48.0 63.5 93.5 52.0 __
132.9 215.3
79.2 211.2
53.6 221.2
*Glucose concentration in mg. per cent. thfr, maternal saphenous vein; AF, amniotic
fluid.
amniotic fluid at term ranged from 41.4 to 119.5 mg per cent with a mean of 77.7 + 26.6 mg. per cent. The glucose concentration differences between amniotic fluid and fetal umbilical arterial plasma at term varied greatly with a range from 29.1 to 93.5 mg. per cent Since the ( mean = 52.2 mg. per cent). amniotic fluid concentrations were fairly constant, the variation in concentration differences was due primarily to variations in fetal plasma glucose concentration. Comment The observations reported in these experiments on arteriovenous differences and gradients between the various body pools were carried out in a conscious resting primate under conditions where stress was minimized as much as practical. Fig. 1 schematically presents the relationships across the primate placenta. The values for the various glucose gradients have been inserted. The exchange of glucose across the monkey placenta is of special interest since it might reasonably be assumed that the differences between various primate placentas including the human placenta are probably slight. However, in contrast with PO, and pC0, gradients, strictly comparable glucose studies in the human or in animals within the primate species are not available at present. Hence, the glucose
gradients reported here cannot yet be used to support this assumption. However, Pedersen’s data in the human’. ’ for total blood sugar differences between the major body fluid pools have been inserted as subscripts in Fig. 1. It is clear that, at least for these gradients, the agreement between the monkey and human data is remarkably close. The arteriovenous differences across the maternal surface can be used to obtain a crude approximation of the quantity of glucose consumed by the monkey uterus and its contents at term. Assuming a uterine blood flow in the term animal of approximately 1 per cent of body weight, a maternal weight of approximately 10 kilograms, and a weight of pregnant uterus and its contents at term of approximately 730 grams, the quantity of glucose utilized by the uterus and its contents per minute can be calculated from the equation below.
(2) Q = (10,000x0.01)
x0.150 mg. per minute
= 15.0
Therefore, the calories provided by glucose alone per day per kilogram of tissue is given below: (3)
0.0150 x 4 x 60 x 24/0.730 GZ 120 calories per kilogram per day
Also the quantity of oxygen required to utilize this arteriovenous difference of glucose (15.0 mg. per cent), is as follows: (4)
6 x 150/180 = 5.0 mM. of oxygen per liter of blood
The actual arteriovenous difference of oxygen found across the maternal surface of the monkey is 3.04 mM. per liter of blood, thus, only 60 per cent (3.04/5.0), of the glucose consumed can be accounted for by oxygen utilization. Presumably the remainder of the glucose consumed is available for synthesis. The decreasing glucose concentration in the amniotic fluid is interesting since it represents one more solute in which concentration has been shown to decrease in amniotic fluid of primates as term approaches.s
Volume Number
88 1
Arteriovenous
The only tissue between the amniotic fluid and the fetal vascular pool in the primates is the amniotic membrane itself. Hence, the concentration gradient between these two body fluids reflects to a certain extent the permeability characteristics of the amniotic membrane to glucose. Assuming fetal plasma glucose concentrations to be fairly constant throughout gestation, our data would suggest that this gradient assumes negligible proportions in early gestation when amniotic fluid concentrations are higher. In reviewing the literature we have been unable to find previous studies on arteriovenous differences across the monkey placenta, or any reports describing the plasma glucose gradients reported here. Similarly, glucose concentrations in monkey cord blood have not previously been reported. However, scattered observations on glucose concentrations in samples obtained from various fetal and maternal vessels have been reported.’ Those values are considerably lower than the concentrations presented here. Differences in experimental technique undoubtedly play a role in accounting for these discrepancies. The experiments in this report were of brief duration and were carried out on well-fed animals without a preoperative period of starvation. AsatianS’ has reported glucose concentrations in adult monkeys
REFERENCES
1.
Hellegers, Battaglia, press.) 2. Battaglia, 3. Somozzvi. 4. Pede&, H.: Acta 5. Pedersen,
ot glucose
37
ranging from 100 to 130 mg. per cent, in close agreement with our results. Chinard and associates9 found whole blood glucose concentrations of 150 mg. per cent and higher in the adult rhesus monkey. From these variations in adult glucose concentrations reported for the monkey and the permeability characteristics of the primate placenta to glucose described by Chinard and associates9 it is clear that meaningful data on fetal glucose concentrations can be obtained only when accompanied by simultaneous maternal samples. Summary Glucose concentrations were determined in maternal arterial, uterine venous, and umbilical arterial blood at term and in the amniotic fluid at selected stages of gestation in a series of pregnant rhesus monkeys. The plasma arteriovenous differences for glucose across the maternal surface of the placenta averaged 14.9 mg. per cent. Plasma glucose concentration gradients across the placenta as a whole averaged 26.6 mg. per cent. The term amniotic fluid glucose concentration was 55.9 + 9.2 mg. per cent. The early amniotic fluid concentrations were 79.2 -L 11.2 mg. per cent. Calculations of glucose gradients between several body fluid pools are described.
6. A., Behrman, R. E., Heller, C., and F. C.: AM. J. OBST. & GYNEC. (In F. C.: J. Pediat. 62: 926, 1963. M.: T. Biol. Chem. 160: 61, 1945. J., Bojsen-Moller, B., and. Paulsen, endocrinol. 15: 33, 1954. J.: Acta endocrinol. 15: 342, 1954.
differences
7. 8. 9.
Battaglia, F. C., Prystowsky, H., Smisson, C., Hellegers, A., and Bruns, P.: Surg. Gynec. & Obst. 109: 509, 1959. Shelley, H. J.: j. Physiol. 153: 527, 1960. Asatiani. V. S.: Usoekhi Sovremennoi Biolorrii 44: 313,’ 1957. Chinard, F. P., Danesino, V., Hartman, W. L., Huggett, A. St. G., Paul, W., and Reynolds, S. R. M.: J. Physiol. 132: 289, 1956.
gradients across the
maternal surface, the placenta, and the amnion of the rhesus monkey (Macaca mulatta) FREDERICK ANDRE
C. E.
CHRISTOPHER RICHARD Baltimore,
BATTAGLIA,
HELLEGERS, J.
M.D.* M.D.+*
HELLER,
BEHRMAN,
A.B.
M.D.*
Maryland
A s P A R T of a study of the primate placenta, determinations of oxygen and carbon dioxide concentrations in fetal blood and in the maternal arterial and venous blood perfusing the maternal surface of the placenta of the pregnant Macaca mulatta have been made and are reported e1sewhere.l Simultaneously, determinations of plasma glucose concentrations in those same animals were made. It is the purpose of this report to present the data on glucose concentrations and to correlate these data with those on the placental exchange of the respiratory gases in the same preparations. In addition, glucose concentration gradients between the amniotic fluid and either the maternal or fetal vascular pool at varying stages of gestation are presented.
First, even in the acute preparations, if due care is taken, the glucose concentrations? per se, may closely approximate the normal steady state values. The importance of such information for any solute has been discussed elsewhere.’ Finally these studies, combined with the oxygen and CO, data presented in the preceding article, were undertaken to provide a more complete evaluation of placental function than has heretofore been possible in the conscious primate under minimal experimental stress. Material
From the Departments of GynecologyObstetrics, and Pediatrics, The Johns Hopkins University and the Department of Gynecology-Obstetrics, University of Puerto Rico. This study was supgorted in part by Research Grant AM-O4240-03 of the National Institutes of Health. *Member, Laboratory of Perinatal Physiology, National Institute of Neurological Diseases and Blindness, National Institutes of Health, San Juan, Puerto Rico.
“*Senior P. Kennedy,
Research Scholar, Jr., Memorial
and
methods
The studies were carried out at the Laboratory of Perinatal Physiology, San Juan, Puerto Rico. The monkeys were selected from a large breeding colony of caged animals on the basis of gestational ages. The criteria used for the gestational timing and selection were as outlined e1sewhere.l The previous report also describes in considerable detail the operative technique. It should be emphasized that variations in operative technique were found to be equally critical for the establishment of normal glucose gradients. Further, normal gradients cannot be obtained under conditions of hypoventilation, starvation ketosis, and stress hyperglycemia. The experiments presented in this report were carried out to determine as closely as
Joseph Foundation. 32
Volume Number
88 1
possible, in an acute preparation, the normal gradients for plasma glucose concentrations across the maternal surface and across the placenta as a whole. Hence, the experiments the data of which form the substance of this report were selected out of all our preparations on the basis of criteria encompassing a clinical appraisal of the animals’ condition before and during the experiment, as well as a biochemical appraisal reflected by pH, pCOo, and oxygen content gradients. A more complete description of these criteria and a presentation of the relevant oxygen, CO,, and pH data obtained from the same animals is given in the preceding article. For the determination of the glucose gradient between the amniotic fluid and the maternal vascular pool in early gestation, amniotic fluid samples were obtained from the long saphenous vein. Term amniotic fluid samples were obtained at the time of cesarean section under direct vision and the simultaneous maternal blood samples were taken from a uterine vein. Plasma glucose concentrations were determined calorimetrically, with glucose oxidase as follows: 100 ~1 aliquots diluted 1:40 with distilled water were deproteinized with barium hydroxide-zinc sulfate by the method of Somogyi3 To 1 ml. of the filtrate was then added 4 ml. of glucose oxidase solution (Worthington Biochemical Corporation’s “glucostat” diluted to final volume 80 ml.). After incubation for 30 minutes at 38’ C. the samples were read at 420 rnp on a Beckman model B spectrophotometer. Results
Maternal arterioverous differences and transplacental gradients. The data for arteriovenous differences and transplacental gradients are presented in Table I. In experiments 1 through 5 the maternal uterine vein concentrations of glucose ranged from 102.1 to 131.5 mg. per cent and the femoral artery glucose concentrations ranged from 132.0 to 151.5 mg. per cent. In two additional animals included in Table I, Q 200 and V 798, although other criteria for a good preparation were met, there were very
Arteriovenous
differences
of glucose
33
high elevations in maternal plasma glucose concentrations, probably related to endogenous epinephrine release. The close agreement in maternal venous glucose concentrations between animals caught with minimal agitation, which were sampled immediately after capture without the use of local anesthesia (Table IV), and those which were sampled within one-half hour after incision at the time of an acute term experiment (Tables I and III), done under local anesthesia (2 per cent procaine, without epinephrine), suggests that in most cases the hepatic mobilization of glucose in the mother was not significant. Five of the experiments (9 through 13) presented in Table I did not meet the criteria for a good preparation and have not been used for calculating normal concentration gradients. In the good preparations the fetal umbilical artery glucose concentrations ranged from 89.0 to 157.5 mg. per cent (Tables I and III). In all such cases the fetal umbilical artery concentration was less than either the maternal arterial or venous concentrations. This was not true for experiments 9 through ,13. The maternal arteriovenous differences for glucose in experiments 1 through 8 ranged from 5.0 to 28.0 mg. per cent with a mean of 14.9 ? 8.8 mg. per cent. Although the number of observations is limited, no obvious correlation between the magnitude of these arteriovenous differences and the absolute arterial or venous concentrations was found. However, Table II shows that if all the data of Table I are used, the arteriovenous differences in preparations with maternal arterial concentrations greater than 200 mg. per cent were significantly greater (28.6 vs. 11.6, P < 0.05) than in the remaining preparations. Within each group no close correlation between the magnitude of the arteriovenous differences and the maternal glucose concentration could be found. The plasma glucose concentration gradient across the placenta as a whole, (the transplacental gradient), was calculated from equation 1.
34
Battaglia
et al
( 1) J/1 [MA + Mv] - Fd = transpiacental gradient Since it might reasonably be expected that the glucose concentration in the fetal capillaries of the placenta was higher than the umbilical arterial concentration, the gradients thus calculated probably represent maximum values. In experiments 1 through 6, the gradients found ranged from 12.3 to 43.7 mg. per cent with a mean of 26.6 it 12.8 mg. per cent (Table I). The variations found could not be correlated with any clear-cut difference in these preparations. However, the common feature of experiments 9 through 13 was the marked variability of the transplacental gradient ranging from 63.2 mg. per cent to 31.3 mg. per cent. From this group of unsatisfactory preparations, only experiment 11 had a “TP” gradient within the normal range, and in this case the arteriovenous difference was larger than any in the normal group.
Glucose concentration differences between amniotic fluid and maternal or fetal vascular pools. Term maternal uterine vein glucose concentrations (Table III, 133.4 mg. per cent), were very similar to the saphenous vein glucose concentrations obtained from animals at 95 to 136 days’ gestation (Table IV, 132.9 mg. per cent). These values did not vary over the duration of
(appoxiniate transplacentol 26+6mTm% (.., 3omgm Xl
: i (-tra#~n across
gradient)
AHNIOTII; ePPLS-----7’-------------dlLlTElWAC gfodient amnlan) i
Transplacental
Fig. 1.
gestations sampled. There was no demonstrable relationship between amniotic fluid glucose concentrations. and maternal plasma However, the glucose concentration in the amniotic fluid early in gestation ranged from 64.0 ma. per cent to 91.5 mg. per cent with a mean of 79.2 + 11.2 mg. per cent compared to term glucose concentrations in the amniotic fluid ranging from 44.5 mg. per cent to 65.0 mg. per cent with a mean of 55.9 t 9.2 mg. per cent. The difference between early amniotic fluid and term amniotic fluid glucose concentrations was 23.3 mg. per cent. This difference was statistically significant (p = < 0.01) One animal, I 193, was sampled at 101 and 115 days’ gestation during which time the amniotic fluid glucose concentration fell from 74.5 mg. per cent to 66.5 mg. per cent. Since the glucose concentrations in the maternal plasma did not differ in the two groups, the maternal vein minus amniotic fluid differences were higher at term, reflecting a decreasing amniotic fluid glucose concentration as term approached. The gradients from the maternal saphenous vein to the amniotic fluid between 95 and 136 days’ gestation ranged from 27.5 mg. per cent to 93.5 mg. per cent with a mean of 53.6 rf: 21.2 mg. per cent. In contrast gradients between maternal uterine vein and
Q@ AMNIO TIC lcwlcaltratian gradtent acmss chdaamnian )
ci3nZatian
prodlent
. : ! Wm.
Volume Number
88 1
Arteriovenous
Table I. Plasma and transplacental
glucose
Cestatioflal aqe
Animal Good
Bad
preparations 1. v 195 2. X 692 3. x 590 4. Q 192 5. H 220 6. X 624 7. Q 200 a. v 798
153 157 158 155 155 153 155 153
preparations 9. 543 B 10. X 706 ii. Q 178 12. X 617 13. x 292
*All tMA, femoral
Table II. difference
are artery; vein;
Animal
No.
<
200
(
195 692 590 220 617
Mean SD+
mg.
No.
/
133.5 146.0 132.5
128.5 131.5 125.0 102.1 130.5
1 la.5 95.0 89.5 89.8
Mean SD z!z *Glucose concentrations tMv, maternal uterine
12.5 43.7 39.2 12.3
21.5 25.5
150.5 305.0 170.5 90.0 193.5
Mean SD k
12.5 28.5 14.9 +a.8
26.6 212.8
134.5 253.5 158.5 102.0 232.5
56.0 23.5 35.5 9.5 15.5
44.0 63.2 29.5 -7.3 -31.3
arterial
glucose
concentration
70
5.0 14.5 7.5 21.5 9.5
132.6
11.6 k6.6
Animal
Mvt
No.
>
difference
between
maternal
arteriovenous
200
)
:! 72908” 543 B X 706 x 292 Q 178
differences
A-V,
with
MA A-V
/
TPt (Glucose)
5.0 14.5 7.5
236.0 193.0
MA
153 157 158 155 153 155
arteriovenous
157.5
133.5 146.0 132.5 151.5 99.5
Gezf;
of glucose
A-V?
Fat
expressed in mg. per cent. Mv, maternal uterine vein; Fn, fetal umbilical artery; TP, Tramplacental glucose gradient = MA + Mr - Fn. 2
Table III. Glucose concentration* and fetal vascular pools at term
v 195 X 692 x 590 H 220 X 624 Q 192
Maternal
Mvt
p
Animal
at term:
Mat
206.5 328.5 205.5 99.5 209.0
Correlation of maternal across placenta MA
gradients
151.5 183.0 248.5 221.5
155 152 157 155 156
glucose concentrations maternal femoral artery and uterine
v X x H X
concentration*
differences
mg.
7%
MA
A-V
248.5 221.5 206.5 328.5 209.0 205.5
12.5 28.5 56.0 23.5 15.5 35.5
236.6
28.6 tl5.8
0.05
<
between
fluid
and maternal
Fnt
AFt
i 28.5 131.5 125.0 130.5 183.0 102.1
118.5 95.0 89.5 98.0 157.5 89.8
65.0 45.0 56.0 44.5 64.0 60.7
+53.5 +50.0 +33.5 +53.5 +93.5 +29.1
+ 63.5 + 86.5 + 69.0 + 86.0 +119.5 + 41.4
133.4 k26.6
108.1
55.9 + 9.2
+52.2 t22.8
+ 77.7 2 26.4
in mg. per cent. vein; Fa, fetal umbillioal
j
amniotic
artery;
AF,
amniotic
fluid.
1
(FrAF)
/
(MTAF)
35
36
Battaglia
January 1, 1964 Am. J. Obst, 6’1 Gynec.
et al.
Table IV. Glucose concentration” differences between amniotic fluid and maternal vascular pools in early gestation
Animal No. J V I I x L J
89 196 193 193 470 248 394
Mean SD k
Gestational age Cdavs) 95 100 101 115 123 125 136
M,+
AF+
/MT-AF)
128.0 118.0 129.0 114.5 145.5 157.5 137.5
91.5 90.5 74.5 66.5 82.0 64.0 85.5 ___
36.5 27.5 54.5 48.0 63.5 93.5 52.0 __
132.9 215.3
79.2 211.2
53.6 221.2
*Glucose concentration in mg. per cent. thfr, maternal saphenous vein; AF, amniotic
fluid.
amniotic fluid at term ranged from 41.4 to 119.5 mg per cent with a mean of 77.7 + 26.6 mg. per cent. The glucose concentration differences between amniotic fluid and fetal umbilical arterial plasma at term varied greatly with a range from 29.1 to 93.5 mg. per cent Since the ( mean = 52.2 mg. per cent). amniotic fluid concentrations were fairly constant, the variation in concentration differences was due primarily to variations in fetal plasma glucose concentration. Comment The observations reported in these experiments on arteriovenous differences and gradients between the various body pools were carried out in a conscious resting primate under conditions where stress was minimized as much as practical. Fig. 1 schematically presents the relationships across the primate placenta. The values for the various glucose gradients have been inserted. The exchange of glucose across the monkey placenta is of special interest since it might reasonably be assumed that the differences between various primate placentas including the human placenta are probably slight. However, in contrast with PO, and pC0, gradients, strictly comparable glucose studies in the human or in animals within the primate species are not available at present. Hence, the glucose
gradients reported here cannot yet be used to support this assumption. However, Pedersen’s data in the human’. ’ for total blood sugar differences between the major body fluid pools have been inserted as subscripts in Fig. 1. It is clear that, at least for these gradients, the agreement between the monkey and human data is remarkably close. The arteriovenous differences across the maternal surface can be used to obtain a crude approximation of the quantity of glucose consumed by the monkey uterus and its contents at term. Assuming a uterine blood flow in the term animal of approximately 1 per cent of body weight, a maternal weight of approximately 10 kilograms, and a weight of pregnant uterus and its contents at term of approximately 730 grams, the quantity of glucose utilized by the uterus and its contents per minute can be calculated from the equation below.
(2) Q = (10,000x0.01)
x0.150 mg. per minute
= 15.0
Therefore, the calories provided by glucose alone per day per kilogram of tissue is given below: (3)
0.0150 x 4 x 60 x 24/0.730 GZ 120 calories per kilogram per day
Also the quantity of oxygen required to utilize this arteriovenous difference of glucose (15.0 mg. per cent), is as follows: (4)
6 x 150/180 = 5.0 mM. of oxygen per liter of blood
The actual arteriovenous difference of oxygen found across the maternal surface of the monkey is 3.04 mM. per liter of blood, thus, only 60 per cent (3.04/5.0), of the glucose consumed can be accounted for by oxygen utilization. Presumably the remainder of the glucose consumed is available for synthesis. The decreasing glucose concentration in the amniotic fluid is interesting since it represents one more solute in which concentration has been shown to decrease in amniotic fluid of primates as term approaches.s
Volume Number
88 1
Arteriovenous
The only tissue between the amniotic fluid and the fetal vascular pool in the primates is the amniotic membrane itself. Hence, the concentration gradient between these two body fluids reflects to a certain extent the permeability characteristics of the amniotic membrane to glucose. Assuming fetal plasma glucose concentrations to be fairly constant throughout gestation, our data would suggest that this gradient assumes negligible proportions in early gestation when amniotic fluid concentrations are higher. In reviewing the literature we have been unable to find previous studies on arteriovenous differences across the monkey placenta, or any reports describing the plasma glucose gradients reported here. Similarly, glucose concentrations in monkey cord blood have not previously been reported. However, scattered observations on glucose concentrations in samples obtained from various fetal and maternal vessels have been reported.’ Those values are considerably lower than the concentrations presented here. Differences in experimental technique undoubtedly play a role in accounting for these discrepancies. The experiments in this report were of brief duration and were carried out on well-fed animals without a preoperative period of starvation. AsatianS’ has reported glucose concentrations in adult monkeys
REFERENCES
1.
Hellegers, Battaglia, press.) 2. Battaglia, 3. Somozzvi. 4. Pede&, H.: Acta 5. Pedersen,
ot glucose
37
ranging from 100 to 130 mg. per cent, in close agreement with our results. Chinard and associates9 found whole blood glucose concentrations of 150 mg. per cent and higher in the adult rhesus monkey. From these variations in adult glucose concentrations reported for the monkey and the permeability characteristics of the primate placenta to glucose described by Chinard and associates9 it is clear that meaningful data on fetal glucose concentrations can be obtained only when accompanied by simultaneous maternal samples. Summary Glucose concentrations were determined in maternal arterial, uterine venous, and umbilical arterial blood at term and in the amniotic fluid at selected stages of gestation in a series of pregnant rhesus monkeys. The plasma arteriovenous differences for glucose across the maternal surface of the placenta averaged 14.9 mg. per cent. Plasma glucose concentration gradients across the placenta as a whole averaged 26.6 mg. per cent. The term amniotic fluid glucose concentration was 55.9 + 9.2 mg. per cent. The early amniotic fluid concentrations were 79.2 -L 11.2 mg. per cent. Calculations of glucose gradients between several body fluid pools are described.
6. A., Behrman, R. E., Heller, C., and F. C.: AM. J. OBST. & GYNEC. (In F. C.: J. Pediat. 62: 926, 1963. M.: T. Biol. Chem. 160: 61, 1945. J., Bojsen-Moller, B., and. Paulsen, endocrinol. 15: 33, 1954. J.: Acta endocrinol. 15: 342, 1954.
differences
7. 8. 9.
Battaglia, F. C., Prystowsky, H., Smisson, C., Hellegers, A., and Bruns, P.: Surg. Gynec. & Obst. 109: 509, 1959. Shelley, H. J.: j. Physiol. 153: 527, 1960. Asatiani. V. S.: Usoekhi Sovremennoi Biolorrii 44: 313,’ 1957. Chinard, F. P., Danesino, V., Hartman, W. L., Huggett, A. St. G., Paul, W., and Reynolds, S. R. M.: J. Physiol. 132: 289, 1956.